Apparatus for degassing fluids



Jan. 9, 1968 3. E. BURNHAM, sR., ET AL 3,362,136

APPARATUS FOR DEGASSING FLUIDS Filed March 30, 1965 2 Sheets-Sheet 1INVENTORS.

GERALD E, BURNHAM, SR. VERGNE E. SMITH ATTOR NEYS.

Jan. 9, 1968 e. E. BURNHAM, SR, ET AL 3,362,136

APPARATUS FOR DEGASSING FLUIDS 2 Sheets-Sheet 2 Filed March 30, 1965 22x TO PUMP INVENTORS.

VERGNE E. SMITH BY ATTORNEYS.

GERALD E. BURNHAMSR.

United States Patent Ofiice 3,362,136 Patented Jan. 9, 1968 ABSTRACT OFTHE DISCLOSURE Oil well drilling mud degassing apparatus with atangential feed conduit for delivering mud through a floatcontrolledelliptical valve onto a helical shelf. The shelf grows progressivelynarrower as it follows its spiral, downward path around the inside wallof the vacuum tank to which it is aflixed. The inside edge of the shelfis downwardly inclined at least 30 from horizontal to cause part of themud to fall in a continuous curtain from said inside edge as theremainder of the mud progresses down :the helical path to an upright,vortex-breaking, deflector plate. Separated gases pass through a misteliminator to a vacuum pump for discharge to atmosphere.

This invention relates to apparatus for degassing fluids, andparticularly to degassing apparatus which forms the fluid into a thincurtain which is subjected to a vacuum to remove the gas.

The problem of degassing fluids exists in many industries. For example,in the oil or gas well drilling industry, drilling mud frequentlybecomes contaminated in the well with natural gas or air. When the mudemerges from the well, the gas must be removed before the mud isrecirculated into the well. Otherwise the gas decreases the weight andviscosity of the mud which will seriously diminish its effectiveness inpreventing blowouts.

Many prior art degassing devices utilize vacuum tanks containing variousstructures for spreading out or breakingup the mud or other fluid toincrease the exposure to the'vacuum. In general, these structures havenot been entirely satisfactory. Some have been complicated with a numberof moving parts which are subject to mechanical failure and clogging.Many of the prior art devices must be cleaned by auxiliary equipmentwhen they are shut down for any appreciable time. If the degassing tankis not immediately cleaned after shutdown, the mud becomes hardrequiring a major operation to remove it. Because of these cleaningproblems, expensive special cleaning jets and apparatus are usuallybuilt into the tank adding greatly to both initial and operatingexpense.

To overcome prior art shortcomings, it is a primary object of thisinvention to provide a highly effective selfcleaning degassing devicewhich is simple and inexpensive and contains a minimum of moving parts.

It is a further object of this invention to provide such a device whichis particularly effective in degassing oil or gas well drilling mud.

These objects and others hereinafter appearing are attained by thepresent invention which generally relates to a degassing system forfluids which comprises in combination a vacuum tank, means forconnecting said tank to a source of vacuum, an elongated guideway withinsaid tank having sides and extending along a line, said line beinginclined from the horizontal such that the fluid to be degassed willflow down the guideway by gravity, said guideway being inclinedtransversely of said line such that a portion of the fluid flowing downthe guideway will flow in a thin curtain off one of said sides of saidguideway allowing the vacuum in the tank to remove the gas from thefalling fluid.

In a preferred embodiment of the invention, the fluid is introduced intothe tank by a tangential flume and is discharged onto the guideway whichis in the form of a helical shelf aflixed to the inner side of the wallof the vacuum tank. Where the helical guideway has more than one turn,it preferably becomes progressively narrower from top to bottom toprevent interference between fluid falling off of successive turns.

The invention having been generally described, a specific embodimentwill be set forth in the accompanying drawings in which:

FIGURE 1 is an isometric view of the novel degassing system mounted inoperating condition relative to a pair of mud tanks;

FIGURE 2 is a cross-section taken through the vacuum tank;

FIGURE 3 is a horizontal section taken substantially on line 33 ofFIGURE 2;

FIGURE 4 is a vertical section taken substantially on line 4-4 of FIGURE2; and

FIGURE 5 is a detailed horizontal section taken substantially on line 55of FIGURE 4.

FIGURE 1 shows a degasification system 10 which includes a fluid tightvacuum tank 2 connected by a conduit having an inlet 3 in a first mudtank 1 which is a part of the mud system of a standard drilling rig. In

.the vacuum tank, the mud is degassed in a manner deof the drilling rig.The vacuum pump 5 is connected to the vacuum tank 2 by line 7, misteliminator 8 and outlet line 9. The mist eliminator 8 is conventionaland its purpose is to condense any stray liquid that is entrained by thegas removed from the mud in vacuum tank 2. Condensate from the misteliminator 8 is returned by line 12 to the bottom of vacuum tank 2.There may be a check valve in line 12 to allow flow only from misteliminator 8 to the tank 2 and preventing flow in the oppositedirection. The degassed mud after passing through the vacuum tank 2 ispumped by mud pump 13 also driven by motor 6 through output line 15 intoa second mud tank 14. The first mud tank 1 and second mud tank 14 areconnected independently of the degasification system by mud trough 16 inthe conventional manner. The entire degasification system 10 is mountedon skid 17 so as to be readily movable.

The specific construction of the degassing tank 2 is best seen inFIGURES 2 through 5. The vacuum tank 2 is in the shape of a verticalcylinder and is sealed against inflow or outflow of fluids exceptthrough desired passages. The mud from mud tank 1 is introduced intovacuum tank 2 through circular inlet conduit 4. The mud to be degassedis deposited by tangential flume 19 on the top of a guideway 18, whichlies along a curved longitudinal line which line is in the general formof a helix. The flow of mud through the conduit 4 is controlled byelliptical valve 22, best seen in FIGURE 3. The elliptical valve 22 ispivotally mounted in the conduit 4 and is rigidly connected by arm 23 tofloat 24. Float 24 moves in response to changes in the liquid level atthe bottom of the tank 2. The float therefore limits the mud inflowthrough conduit 4 according to the rate at which cmud is removed fromthe tank. With the control valve located in the mud inlet line, ratherthan in the vacuum line, the mud flow may be cut off while vacuum isstill applied inside the tank. The helical guideway 18 preferably is aflat shelf havlng an 1nner edge 25 and an outer edge 26. The outer edge26 is aflixed to the side wall 21 of the vacuum tank 2 by welding or anyother appropriate connection. The guideway 18 is inclined bothlongitudinally (circumferentially) and transverse to its longitudinalpath (radially) so that the mud flowing down the guideway will fall in acontinuous thin curtain off the inner edge 25. In the particularembodiment shown, the guideway has a pitch of twelve inches per turnwith a tank five feet in diameter. The radial inclination of theguideway is at least 30 from the horizontal. It has been found thatthese inclinations are satisfactory in the degassing of most drillingmuds. It will be understood that these specific inclinations may varydepending upon many factors such as the viscosity of the fluid beingdegassed and the velocity at which it is introduced onto the guideway.

The inclination of the helical guideway 18 transverse to itslongitudinal (circumferential) dimension must be selected so as tocounteract the action of centrifugal force tending to move the mudflowing down the guideway against the outer wall 21 of the vacuum tank2. In addition, the inclination must be sufficiently greater than theinclination necessary to balance the centrifugal force so that some ofthe mud will fall as a contiuous curtain from the inner side 25.

As the mud falls in a continuous curtain off the inner edge 25 of thehelical guideway 18, the vacuum maintained in the tank through line 9will remove gas trapped in the mud. In order to prevent interferencebetween fluid falling off of succesive turns of the helical guideway 18,the guideway is made progressively narrower from top to bottom. Thus,the inside diameter of the helical shelf becomes progressively greater.Preferably, all of the mud will have been discharged from the helicalguideway at about the time the flow of mud reaches the bottom of theguideway. However, any mud which is discharged longitudinally from thebottom of the guideway will strike upright deflector plate 27 and falldirectly to the bottom of the tank. The deflector plate 27 is alignedwith the end of the guideway 26 and prevents formation of a vortex bymud leaving the end of the guideway.

The mud collected in the bottom of the tank is re moved from the tankthrough outlet pipe 28 by the pump 13. The gas removed from the mud isejected through outlet 9 and is passed through mist eliminator 8 asdescribed previously.

Mist eliminator 8 is of standard construction and is therefore not shownin detail. Mist eliminator 8 is placed at the level of the top of thevacuum tank 2 so that the condensate from the mist eliminator may flowby gravity back into the vacuum tank 2 through condensate line 12.Preferably, a check valve is located in the condensate line 12 to limitflow to the direction toward the tank 2.

In operation, mud is forced from mud tank 1 through line 4 by thedifferential pressure of the atmosphere acting on the surface of the mudin tank 1 and the vacuum in the vacuum tank 2. The mud passes throughthe elliptical control valve 22 and flume 19 and is discharged onto thehelical guideway 18. A portion of the mud falls in a continuous curtainoff the inner edge 25 as the mud moves down the guideway. The gas isremoved from the falling curtain of mud by the vacuum produced in thetank by the vacuum pump acting through line 9. The removed gas passesout of the tank through line 9, through the mist eliminator 8, and isexhausted to the atmosphere or otherwise disposed of by vacuum pump 5.The degasified mud is drawn from the bottom of the tank 2 through outlet28 by pump 13 and pumped into the second mud tank 14. If thedegasification system for any reason should be shutdown, the mud in thetank will continue to flow down the guideway and out the outlet 28, thusmaking the tank self-cleaning.

It should be noted that inside the tank 2 there are no moving partsother than the simple valve 22. The degasification is highly eflicientsince the application of vacuum to the thin falling curtain of mudlowers the pressure of the mud and will enable all or nearly all of thegas to escape.

Cir

It is of course possible to make the guideway 18 in a configurationother than a true helix. For example, it would be possible to vary thepitch of the helix from one turn to the next, and to vary theinclination of the guideway 18 to match the pitch.

Moreover, while the invention has been described with reference to apreferred specific embodiment, many other modifications may be made bypersons skilled in the art without departing from the scope of theinvention which is defined solely by the appended claims.

What is claimed is:

1. In a degasification system for fluids, the combination whichcomprises:

a vacuum tank,

means for connecting said tank to a source of vacuum,

a single, continuous guideway within said tank having sides andextending along a line,

said line being generally in the shape of an upright helix,

the pitch of said helix being such that the fluid to be degassed willflow down the guideway by gravity,

said guideway being inclined transverse to said line toward the axis ofsaid helix such that a portion of the fluid flowing down the guidewaywill flow in a thin curtain off the inner side of said helix, andwherein said helix extends longer than one complete turn, and the widthof the guideway at any point below the uppermost turn is less than thewidth of the guideway vertically above that point on the preceding turnof the helix so that the discharge from each turn above the lowermostturn will not interfere with that portion of the fluid being dischargedfrom the next lower turn.

2. The combination of claim 1 wherein the width of said guideway isgradually decreased from its top to its bottom.

3. The combination of claim 2 further comprising an upright deflectorplate mounted in the path of the fluid being discharged from the bottomof said guideway.

4. A combination of claim 2 wherein said tank has a gas dischargeconduit and a mist eliminator connected to said conduit, said misteliminator having a condensate return connection to said tank, said misteliminator being positioned above the level of the liquid in said tankso that the condensate will return to the tank by gravity.

5. In a drilling mud degassing system the combination which comprises:

a cylindrical tank having a vertical axis,

means to connect said tank to a vacuum pump, v

a continuous helical mud guideway mounted in said tank with its outeredge engaging the interior of the wall of said tank,

means for introducing said drilling mud into said tank and depositingthe mud onto the top of said guidey,

said means for introducing including a circular inlet conduit and anelliptical valve in said conduit controlled by a float within the vacuumtank,

means rigidly connecting said float to said valve, and

said guideway having an inner edge sufficiently lower than said outeredge so that a portion of the drilling mud flowing down the guidewaywill freely fall from said inner edge toward the bottom of said tank sothat exposure of said falling curtain of mud to the vacuum will effectremoval of gas from the mud.

6. In a degasification system for well bore fluids and the like, thecombination comprising:

(a) a vertically positioned tank;

(b) said tank having openings at its upper and lower ends for receivingand discharging well bore fluids;

(c) vacuum means mounted with said tank;

(d) said opening at the upper end of said tank being positionedtangentially relative to said tank;

(e) a single, continuous spiral shelf having two edges, said first edgebeing secured with the inner surface of said tank, and said second edgebeing positioned below said first edge;

(f) said shelf extending from adjacent said opening at the upper end ofsaid tank to adjacent said opening in the lower end of said tank whereinfluids enter tangentially into and relative to said tank to therebyfollow the path of said spiral shelf until gravity urges the fluid oversaid second edge of said shelf to thereby cause the fluid to fall to thebottom of said tank whereby the fluids are removed through said openingin the lower end of said tank and vapors are released from the fallingfluid to be removed by said vacuum means; and

(g) said spiral shelf decreases in width from adjacent said opening inthe upper end of said tank to adjacent said opening in the lower end ofsaid tank.

7. The structure as set forth in claim 6 including:

(a) a float member positioned in said tank and floating on the fluid insaid tank;

(b) an elliptical closure member pivotally mounted in said tangentialopening in the upper end of said tank; and

(c) an arm mounted between said float member and said elliptical closuremember wherein a rise in fluid level in said tank thereby causes saidfloat member to rise which causes said elliptical closure member toclose said opening in the upper end of said tank and wherein said vacuummeans is unafiected by rising fluid level in said tank.

8. In a drilling mud degassing system, the combination which comprises:

(a) a cylindrical tank having a vertical axis;

(b) means to connect said tank to a vacuum pump;

(c) a continuous helical mud guideway mounted in said tank with itsouter edge engaging the interior of the wall of said tank; l i

(d) said helical guideway extending further than a (e) means forintroducing said drilling mud into said tank and depositing the mud ontothe top of said guideway; and

(I) said guideway having an inner edge sufliciently lower than saidouter edge so that a portion of the drilling mud flowing down theguideway will freely fall from said inner edge toward the bottom of saidtank so that exposure of said falling curtain of mud to the vacuum willeffect removal of gas from the mud.

References Cited 1 UNITED STATES PATENTS 714,793 12/ 1902 Gathmann210-512 2,333,961 11/ 1943 Sweeny 209-144 2,913,068 11/1959 Mistarz eta1 55-204 3,226,916 1/1966 Bradford et al. 55-193 3,241,925 3/1966Griffin et a1. 55-193 X FOREIGN PATENTS 1,332,477 6/ 1963 France.1,142,097 1/1963 Germany.

SAMIH N. ZAHARNA, Primary Examiner.

, REUBEN FRIEDMAN, Examiner. R. BURKS, Assistant Examiner,

